Whether in a next generation network (NGN) or an Internet protocol (IP) multimedia subsystem (IMS) network, a media gateway is configured to complete a calling process under the control of soft switch (SS) or a call session control function (CSCF).
With the continuous development and evolution of the NGN, and for the sake of operators' development, user access equipments tend to become smaller, and some small media gateways may be deployed under the NGN or IMS core network equipments. Each media gateway accesses a core network through protocol interfaces such as an H.248 protocol or Session Initial Protocol (SIP) and the like; however, the media gateway and the core network equipment may be out of control due to various reasons, such as protocol interface interruptions.
Presently, although some devices can exchange internally in the case of losing contact with the core network control equipment, the range is only limited within the equipment; however, most calls to other gateways cannot be guaranteed. Although some devices are equipped with escape interfaces, both additional hardware interfaces and additional external network interfaces are needed to be configured, which increases the cost, and increases the complexity of networking and network management.
Particularly, for those important large enterprise network users, conversations within an enterprise should be guaranteed. A large number of users within an enterprise network may belong to a number of different media gateways; if the protocol service interface between a certain media gateway and the core network equipment interrupts, then the media gateway is basically isolated from the enterprise network, therefore, the users of this media gateway cannot communicate with other users of the enterprise network.